Neurally mediated hypotension (NMH) and positional orthostatic tachycardia syndrome (POTS): Part I: Associated neurological abnormalities.
Michael J. Rosner, Royce K. Bailey, Jorge Flechas

INTRODUCTION: NMH and POTS are cardiovascular dysautonomias. The diagnosis is confirmed by tilt table examination (phase I-without isoproterenol) or with tachycardia induced by isoproterenol (phase II). Neuroanatomically, these conditions relate to the brainstem and spinal cord, but have not usually been viewed as due to structural changes in the regions. OBJECTIVE: To define associated neurological abnormalities in patients who may be candidates for surgical decompression, to document symptomatic outcome at one-year after surgery (part II) and to document radiological differences between control and this subset of FM patients (part III). Methods: 37 patients had undergone a positive tilt table examination. Each prospectively underwent an evaluation that included a detailed neurological history and examination, protocol craniocervical MR, and detailed questionnaire regarding symptoms. Results:  Patients had been symptomatic for > 10 years and on disability for an average of 4.9 years.  Cranial Nerve deficits: 14/37 demonstrated unilateral or bilateral Horner’s syndrome.  21/37 had CN V abnormalities including absent corneal reflexes.  7/17 demonstrated CN VII abnormalities (not including dry eyes, dry mouth, or hyperacusis) and 17/37 had abnormalities of hearing (not including tinnitus).  20/37 had CN IX, X, XI abnormalities, most commonly absent gag reflex and oropharyngeal sensory changes. Abnormalities of convergence, nystagmus, head tilt, skew deviation, esophoria and tongue weakness were common.  Upper extremity motor deficits were identified in 36/37 and 35/37 in the lower extremities. Hyper-hypotonia and atrophy were frequent.  32/37 had abnormalities to pin, touch, vibration or temperature sensation.  24/37 demonstrated hyperreflexia, and 17/37 demonstrated hyporeflexia.  34/37 had abnormalities of gait, 27/37 a positive Romberg’s sign and Babinski’s and Hoffman’s sign were present in 18 and 8 of the 37 respectively. Conclusion:  Neurological deficits can be identified in those patients with NMH/POTS. These deficits  localize to the brainstem .and upper cervical spinal cord and when identified should lead to a detailed  radiological evaluation of these regions in search of remedial compression. 

INTRODUCTION:  Neurally mediated hypotension is a syndrome characterized by severe orthostasis and often accompanied by Positional Orthostatic Tachycardia Syndrome (POTS).  Particularly prominent amongst these patients are  cardiovascular symptoms such as dizziness, palpitations, non-cardiac chest pain, Raynaud’s phenomena, and others.  We have recognized in many of these patients neurological complaints of numbness, weakness, ataxia, dysphagia, tinnitus, visual changes and multiple other dysautonomias.  Often, these patients have had their symptoms attributed to hysteria, malingering, depression or other psychosomatic origins.  Because of the question of non-organic complaints, we limited this study to those with a positive tilt table test for Neurally Mediated Hypotension (NMH), Positional Orthostatic Tachycardia Syndrome (POTS) or both. 

OBJECTIVE: To examine the occurrence of neurological deficit amongst individuals with tilt table proven Neurally Mediated hypotension and/or Positional Orthostatic Tachycardia Syndrome (POTS).  METHODS:  Fifty-two patients with the diagnosis of neurally mediated hypotension and /or positional orthostatic tachycardia syndrome were referred for the possibility of surgical intervention. They underwent protocol neurological examinations (part 1), a protocol MR scan evaluation of the craniocervical region (part 2), and prospectively completed questionnaires grading a list of symptoms which were also used at follow-up examinations (part 3).  Cranial nerve and brainstem functions: Each nerve was assessed for normal versus impaired function. Additional observations included the presence or absence of Horner’s syndrome, convergence deficits and nystagmus.  Hyperacusis, dry eyes, and dry mouth were not recorded as VII nerve abnormalities. Motor function was graded using the MRC scale of 0-5 for each major group of the upper and lower extremities. Data were summarized as showing normal or abnormal strength for the upper and lower extremities separately.  Grip  strength  was  measured as the average of each of three trials on a hand dynamometer Sensory function included pinprick, light touch in each dermatome; temperature sensation (cool) and vibration for multiple points in each extremity.  Data were recorded as normal or abnormal. Gait was assessed in terms of a standard walk, heel walking, tip-toe walking, and tandem gait.  Data were summarized as normal or abnormal.  Romberg’s test was recorded as “0” for normal, 1+ for a slight sway, 2+ for consistent sway, 3+ for severe unsteadiness which did not lead to a fall, and 4+ for those who fell or had to be caught. Reflexes were graded 0-4 with “2” being normal.  Hyporeflexia and hyper-reflexia were summarized separately. Analysis was through Systat 7.0 and/or Microsoft Excel XP.

Cranial Nerve Abnormalities:
Nystagmus                                  64%      Usually fine or rotatory, more
                                                      prominent in extension
Convergence abnormal   43%                 Often asymmetric left eye
                                                      usually worse              
Horner’s syndrome          31%           
Absent corneal reflex       37%                Uni- or bilateral
Other V abnormality        69%                 Often intraoral
 VII abnormality             20%      Most apparent with testing of                         
                                                      orbicularis oculi
VIII abnormality                46%
IX-X abnormality               60%      Usually included uni- or
                                                       bilaterally absent gag reflex
Motor Function:
Upper extremities                        86%     Usually multiple groups
Lower extremities                       94%     Most often iliopsoas, usually
Grip strength:
Right                            28.2 +/- 9.7 Kg (Median = 27.2)
Left                              27.1 +/- 9.5 Kg (Median = 24.5)
Sensory function:               88%    Multiple modalities were
                                                         usually abnormal
Deep tendon reflexes:
Normal:                                                15%
Hyper-reflexia                     52%
Hypo-reflexia                      19%
Both Hyper- and Hypo-      14%

Pathological reflexes:
Babinski’s response  Normal               40%
            Unilateral 14%        
            Bilateral                     6%
            Unilateral 15%
            Bilateral                   25%

Hoffman reflex
            Absent (normal)      76%
            Uncertain 6%
            Unilateral 16%
            Bilateral                   2%

Gait:                                     92%         Usually spasticity,
                                                            ataxia, wide based
            Normal or “Trace”    35%
                            2-3+         55%
                            4+            10%

DISCUSSION: In patients with the dysautonomias, NMH/POTS, neurological abnormalities are common and localized to the brainstem and upper cervical spinal cord.  These abnormalities are frequently subtle, and require significant time and experience to define.  However, they point directly to a coherent anatomical focus, which can explain many of the symptoms and encourage the search for correctible lesions. The brainstem not only is adequate explanation for symptoms such as dysphagia, dysphonia, difficulty with balance and others, but it also harbors the centers for cardiovascular control, gastrointestinal control, respiration and the reticular activating system (see part 2 & 3).  The latter is particularly important with regard to sleep, arousal, attention and the subsequent incorporation of memory.  The lower medulla also is the source of origin for descending nociceptive control fibers, which originate in the nucleus raphe magnus and paragigantocellularis. In those with NMH and related cardiovascular abnormalities, neurological abnormalities should invoke a search for treatable lesions: that search should focus on the upper spinal cord and brainstem based upon the observations presented here.

CONCLUSION: In patients with positive tilt table examinations for NMH/POTS, neurological abnormalities were common. These abnormalities center about the lower brainstem and upper spinal cord.

Abstract presented at American Assoc of Neurological Surgeons Annual Meeting 2002.

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